The solvation of chloride by methanol - surface versus interior cluster ion states

A combined experimental and theoretical structural study of methanolated ch loride anions has been conducted, utilizing infrared vibrational spectrosco py and ab initio electronic structure calculations. These results represent the first such study for an anion with a nonaqueous solvent. The principal question addressed is whether the cluster ions assume structures reflectin g surface or interior solvated states. The vibrational spectra in the O-H s tretching regions, for Cl-(CH3OH)(1-8,10,12), and calculated O-H vibrationa l bands for Cl-(CH3OH)(1-4), consistently indicate that the chloride anion undergoes surface solvation. The behavior is remarkably similar to that of hydrated anions (chloride, bromide, and iodide) with large polarizabilities . This suggests that the asymmetric hydration of these anions lies not nece ssarily in the nature of the solvent, but in the nature of the anion. (C) 1 999 American Institute of Physics. [S0021-9606(99)00319-0].